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mm: khugepaged: skip huge page collapse for special files
commita4aeaa06d4
upstream. The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2]. This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface. [shy828301@gmail.com: fix vm_file check [3]] Link: https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@mail.gmail.com/ [1] Link: https://lore.kernel.org/linux-mm/000000000000c6a82505ce284e4c@google.com/ [2] Link: https://lkml.kernel.org/r/CAHbLzkqTW9U3VvTu1Ki5v_cLRC9gHW+znBukg_ycergE0JWj-A@mail.gmail.com [3] Link: https://lkml.kernel.org/r/20211027195221.3825-1-shy828301@gmail.com Fixes:99cb0dbd47
("mm,thp: add read-only THP support for (non-shmem) FS") Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Yang Shi <shy828301@gmail.com> Reported-by: Hao Sun <sunhao.th@gmail.com> Reported-by: syzbot+aae069be1de40fb11825@syzkaller.appspotmail.com Cc: Matthew Wilcox <willy@infradead.org> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Song Liu <songliubraving@fb.com> Cc: Andrea Righi <andrea.righi@canonical.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 10 additions and 7 deletions
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@ -443,21 +443,24 @@ static bool hugepage_vma_check(struct vm_area_struct *vma,
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if (!transhuge_vma_enabled(vma, vm_flags))
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return false;
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if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) -
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vma->vm_pgoff, HPAGE_PMD_NR))
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return false;
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/* Enabled via shmem mount options or sysfs settings. */
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if (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) {
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return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
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HPAGE_PMD_NR);
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}
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if (shmem_file(vma->vm_file))
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return shmem_huge_enabled(vma);
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/* THP settings require madvise. */
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if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always())
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return false;
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/* Read-only file mappings need to be aligned for THP to work. */
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/* Only regular file is valid */
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if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file &&
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(vm_flags & VM_DENYWRITE)) {
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return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
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HPAGE_PMD_NR);
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struct inode *inode = vma->vm_file->f_inode;
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return S_ISREG(inode->i_mode);
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}
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if (!vma->anon_vma || vma->vm_ops)
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